Polymerization process



United States Patent 3,380,972 POLYMERIZATION PROCESS John R. Le Blane,Wilbraham, and Joel Fantl, Springfield, Niass, assignors to MonsantoCompany, St. Louis, Mo., a corporation of Delaware No Drawing.Continuation-impart of application Ser. No. 162,957, Dec. 28, 1961. Thisapplication July 12, 1965, Ser. No. 471,466

17 Claims. (Cl. 260-785) ABSTRACT OF THE DISCLOSURE Disclosed herein isa novel process by which maleic monomer is heated to a temperature of atleast 100 C. and vinylidene monomer is slowly added thereto withagitation while maintaining in the reaction mixture a specifiedconcentration of a free radical generating polymerization initiator anda specified concentration of a molecular weight regulator whichcorresponds to the formula:

Izl!

wherein R is a cyclic organic radical to which is joined at a carbonatom of an alicyclic ring having at least four members, and wherein Rand R are independently selected from the group consisting of hydrogenand an alkyl radical.

This invention is a continuation-in-part of copending application S.N.162,957, filed Dec. 28, 1961, now abandoned, and relates to a masspolymerization process and more particularly to a mass polymerizationprocess for preparing water soluble, low molecular weight interpoly-Iners of a maleic monomer and a vinylidene monomer interpolymerizabletherewith, typically interpolymers of maleic anhydride and styrene.

There is growing interest in water soluble, low molecular weightinterpolymers of maleic monomers such as maleic anhydride, maleic acidand half esters of maleic acid. In particular, there is growing interestin water soluble interpolymers of styrene and maleic anhydride whichhave molecular weights of less than 10,000. Heretofore, to prepare suchlow molecular weight interpolymers of maleic monomers it has beennecessary to prepare such interpolymers by solution polymerizationprocesses, which processes are relatively costly. It would be desirableto have available to the art alternate low cost processes for preparingsuch low molecular weight interpolymers of maleic monomers and inparticular it would be desirable to have available a mass polymerizationprocess for preparing such water soluble, low molecular weightinterpolymers.

It is an object of this invention to provide a novel process forpreparing water soluble, low molecular weight interpolymers of maleicmonomers.

A further object of this invention is to provide a novel masspolymerization process for preparing water soluble low molecular weightinterpolymers of maleic monomers.

Other objects and advantages of this invention will be apparent from thefollowing detailed description thereof.

The above and related objects are attained by a novel process in whichthe maleic monomer is heated to a tem- 3,380,972 Patented Apr. 30, 1968perature of at least C. and the vinylidene monomer is slowly addedthereto with agitation while maintaining in the reaction mixture :1specified concentration of a free radical generating polymerizationinitiator and a specified concentration of a molecular weight regulatorwhich corresponds to the formula:

wherein R is a cyclic organic radical to which =CRR" is joined at acarbon atom of an alicyclic ring having at least 4 members, and whereinR and R" are independently selected from the group consisting ofhydrogen and an alkyl radical.

The following examples are set forth to illustrate more clearly theprinciple and practice of this invention to those skilled in the art.Where parts or quantities are mentioned, they are parts or quantities byweight.

Example I To a stirred reaction vessel equipped with a dropping funnelare charged 81 parts (0.62 mol) of methyl acid maleate and 1.6 parts ofterpinolene. The reaction mixture is heated to a temperature of 108 C.and there is added thereto with agitation 66 parts (0.63 mol) of styrenehaving dissolved therein 1.6 parts of terpinolene, 0.5 part ofbeta-nitrostyrene, 0.7 part of benzoyl peroxide and 0.2 part of ditertiary butyl peroxide. The addition of the styrene monomer solution tothe maleic monomer is made at a slow continuous rate over a period of 2hours, this rate of styrene monomer addition being approximately twicethe rate at which the styrene monomer in the reaction vessel is beingpolymerized. The resulting reaction mixture is then transferred to asealed reaction vessel and heated for 2 hours at 130 C. and finally for5 hours at C. The specific viscosity of a 15% solution of the resultinginterpolymer composition in methyl ethyl ketone is 7.7. The reactionmixture is completely soluble in a 28% aqueous ammonium hydroxidesolution.

Example II To a stirred vessel are charged 49 parts (0.5 mol) of maleicanhydride, 86 parts (0.5 mol) sec-butyl acid maleate and 3.0 parts ofterpinolene. The mixture is heated to 100 C. and 104 parts (1.0 mol) ofstyrene together with 1.8 parts of di-tbutyl peroxide and 9.0 parts ofterpinolene are added gradually over a 2.5 hour period. The mixture istransferred to a suitable reaction vessel where the polymerization isfinished at 100-150 C. over an additional 7 hours. The specificviscosity of a 15 solution of polymer composition in methyl ethyl ketoneis 4.6 and the interpolymer is completely soluble in aqueous ammonia.The fact that the interpolymer is completely soluble in aqueous ammoniaindicates that the terpinolene is chemically combined in the polymerproduct.

Example III The same procedure is used as in Examples 1 and II exceptthat 78.4 parts of maleic anhydride, 173 parts of butyl Cellosolve 1acid maleate and 51 parts of terpinolene are charged to the reactor and166 parts of styrene and 4.0 parts of di-t-butyl peroxide are addedgradually to the maleic monomers over a 3 hour period. After completingthe polymerization a polymer composition with a specific viscosity of1.9 and a number average molecular Weight of 1200 is obtained. Ahomogeneous l Butyl Cellosolve is the mono-n-butyl ether of ethylenegycol.

3 polymer solution of borderline water solubility is prepared bydissolving 40 parts of the reaction mixture in 22 parts of 28% ammoniumhydroxide and 38 parts of water. The Brookfield viscosity of thissolution is 52 poises.

Example IV Example V 98 parts of maleic anhydride, 104 parts of styrene,1.8 parts di-t-butyl peroxide and parts of terpinolene are allowed toiaterpolymerize as in Example 111. An interpolymer composition with aspecific viscosity of 7.7 is obtained. The reaction mixture iscompletely soluble in a 28% aqueous ammonium hydroxide solution.

Example V1 This example illustrates that more than 1 mol. of styrene permol of maleic acid derivative can be used.

93.5 parts of Z-ethylhexyl acid maleate, 70.5 parts of isobutyl acidmaleate and 23 parts of terpinolene are charged to a stirred kettle. 119parts of styrene (40 mol percent excess) and 2.8 parts of did-butylperoxide are added over 3 hours. The reaction is stirred for 7 hourstotal at l25-l50 C. to complete polymerization. The interpolymercomposition has a specific viscosity of 1.9. The reaction product iscompletely soluble in a 28% aqueous ammonium hydroxide solution.

The process of the invention is carried out in such a manner that themaleic monomer and the vinylidene monomer are interpolymerized at atemperature of at least 100 C. (and below the decomposition temperatureof the interpolymer being formed) and in the presence of at leastminimum specified concentrations of a free radical generatingpolymerization initiator and a molecular weight regulator of a specifiedchemical type. In ad dition, in at least the initial stages of thepolymerization, i.e., in the period in which at least the first 20 molpercent of the maleic monomer has polymerized, the maleic monomer ispresent in massive excess of the vinylidene monomer in thepolymerization zone. By massive excess is meant a mol ratio of at least5:1. Stated in another way, the concentration of the vinylidene monomerin the reaction medium will be relatively low.

To establish such reaction conditions, at least a substantial portionand preferably all of the maleic monomer is initially charged to thereaction vessel and heated to a temperature of at least 100 C. Themaleic monomer is then stirred and the vinylidene monomer is addedthereto at a slow uniform rate. Specifically, the vinylidene monomer isadded to the reaction zone at a rate not greater than 5 times the rateat which the added vinylidene monomer is being polymerized. In apreferred embodiment of the invention the vinylidene monomer is added at-a rate not more than twice the rate at which the vinylidene monomer isbeing polymerized and more especially at a rate substantially equal tothe rate at which the added vinylidene monomer is being polymerized. Therate at which the vinylidene monomer is charged to the reaction zonesassures that the maleic monomer will be present in massive excess of thevinylidene monomer throughout a substantial portion of thepolymerization reaction.

When the polymerization is run by adding the vinylidene monomer to themaleic monomer at substantially the rate at which the added vinylidenemonomer is being polymerized, the entire polymerization will be run in astirred reaction vessel. When the vinylidene monomer is added to themaleic monomer at a rate faster than the added vinylidene monomer isbeing polymerized, the reaction mixture can'be transferred to anunstirred reactor after the addition of the vinylidene monomer iscompleted. When such a transfer in reaction vessel is made, it usuallywill be made after 30 or preferably 50 mol percent or more of the totalmonomers have polymerized.

It will be noted that no solvent is used in the process of thisinvention, nor is any monomer present in excess to serve as a solvent.Thus, the present process is a true mass polymerization process and isnot to-be confused with solution polymerization process of the priorart, as represented by Lundquist, U.S. 2,383,399.

The reaction is carried out under conditions such that the free radicalgenerating polymerization initiator is present in the polymerizationreaction in the amount of at least about 0.5% and preferably in theamount of about 0.510% and more especially 1.04.0%, based upon thevinylidene monomer that has been added to the maleic monomer. Typicalexamples of the free radical generating polymerization initiators whichmay be employed include benzoyl peroxide, ditertiary butyl peroxide,tertiary butyl hydroperoxide, lauroyl peroxide, tertiary butylperbenzoate, tertiary butyl peracetate, azoisobutyronitrile, cumenehydroperoxide, etc.

The reaction is also carried out in the presence of a specific type ofmolecular rate regulator which is present in the reaction mixture in theamount of at least about 0.5% and preferably in the amount of at leastabout O.530% and more especially 520%, based upon the vinylidene monomerthat has been added to the maleic monomer. This upper limit of 30% ofmolecular weight regulator based upon the vinylidene monomer has beenfound to be about the maximum at which water soluble reaction productsoccur. When this limit is exceeded the products are at least partiallywater insoluble and, thus, commercially unacceptable.

The free radical generating polymerization initiator and the molecularweight regulator may be initially charged to the reaction with themaleic monomer, may be added to the polymerization with the vinylidenemonomer or may be split therebetween. Preferably, a substantial portionand optionally all of the molecular weight regulator required in thereaction is charged with the maleic monomer and the free radicalgenerating polymerization initiator is charged to the polymerizationreaction with the vinylidene monomer.

The molecular weight regulators employed in the process of the inventionconform to the formula:

wherein R is a cyclic organic radical to which =CR'R" is joined at acarbon atom of an alicyclic ring having at least 4 members, and whereinR and R" are independently selected from the group consisting ofhydrogen and an alkyl radical.

Exemplary of utilizable molecular weight regulators are methylenecyclobutane, methylene cyclopentane, caryophyliene, pulegone,terpinolene, beta-terpinene, pseudolimonene, bet'a-phellandrene, 1(7),-4(8)-p-menthadiene, 2,4(8)-'p-menthadiene, sabinene, beta-pinene,camphene, alpha-fenchene, beta-fenchene, and mixtures thereof, as wellas many other compounds which satisfy the requirement of correspondingto the above formula, especially the compounds wherein R and R" of theformula represent hydrogen or a methyl group.

The preferred molecular weight regulators are cyclic terpenes whichcontain a 6-membered alicyclic ring, monocyclic terpenes beingespecially preferred. Although such cyclic terpenes can advantageouslybe employed in the form of commercial terpene mixtures, it is usuallypreferred to avoid using commercial terpene mixtures wherein themolecular weight regulator of the invention is contaminated by anysubstantial amount of impurities other than unsaturated cyclic terpenes.Other impurities can be present without destroying the effectiveness ofthe molecular weight regulator, but they may cause undesirable efiects,such as foaming. If desired, other types of molecular weight regulatorssuch as betanitrostyrene and mercaptans can be used in conjunction withthe primary molecular weight regulators.

The maleic monomers employed in the practice of the invention areselected from the group consisting of maleic anhydride, maleic acid andhalf esters of maleic acid and a 1-18 carbon atom monohydric alcohol.Typical examples of such monomers, in addition to maleic anhydride andmaleic acid, include methyl acid maleate, secondary butyl acid maleate,butyl Cellosolve acid maleate, Z-ethylhexyl acid maleate, octadecyl acidmaleate, etc. In one embodiment of the invention, the maleic monomerpolymerized will consist of a mixture of methyl acid maleate andsecondary butyl acid maleate in which the secondary butyl acid maleateconstitutes in excess of 50 Weight percent of the mixture.

The vinylidene monomers employed in the process of the invention can beany of the vinylidene monomers which are known to polymerize with maleicmonomers of the type described in the paragraph above. Typicalvinylidene monomers that can be employed include vinyl esters of organicand inorganic acid such as vinyl acetate, vinyl stearate, vinylchloride; vinylidene aromatic compounds such as styrene, vinylnaphthalene and the ring-alkyl and ring-halogen substituted derivativesthereof, e.g., vinyl toluene, vinyl xylene, 2,4-dimet'hylstyrene,chlorostyrene, 2,5 dichlorostyrene, 2-methyl-4-chlorostyrene, etc.;vinyl alkyl ethers, e.g., vinyl methyl ether, vinyl isobutyl ether,etc., vinylidene heterocyclic compounds such as vinyl pyridine, etc.,and mixtures of two or more of said vinylidene monomers. When thevinylidene monomer employed has an atmospheric boiling point of lessthan 100 C., it is obvious that the reaction will have to be run in asealed pressure-resistant autoclave.

The maleic monomer and the vinylidene monomer will be employed in theratio of 1-2 and preferably 11.5 molar portions of the vinylidenemonomer per molar portion of the maleic monomer. In an especiallypreferred embodiment of the invention the vinylidene monomer and themaleic monomer will be employed in an essentially equimolar ratio.

Depending upon the reaction temperature, the concentration of the freeradical generating polymerization initiator, and the concentration ofthe molecular weight regulator it is possible to prepare interpolymersof maleic monomers which have a number average molecular weight of lessthan 10,000 and in some cases molecular weight as low as 1,000 or evenslightly less. As is known in the art, interpolymers of maleic monomershaving molecular weight in this range have utility for a number ofpurposes, particularly in the preparation of coating compositions.

The molecular weight regulators employed in the process of the inventioncontain olefinic unsaturation and it is believed that, to a degree atleast, the molecular Weight modifier actually interpolymerizes with themaleic monomer and/ or the vinylidene monomer. This belief isstrengthened by the observation that the polymeric products obtained bythe process of the invention are completely soluble in aqueous ammonia.If any substantial quantity of the molecular weight regulator werepresent in a free-form it would be insoluble in the aqueous ammonia.Thus, in all probability, the polymeric products obtained by the processof the invention are either terpolymers of the maleic monomer, thevinylidene monomer and the molecular weight regulator and/ or a blend of(1) an interpolymer of the maleic monomer and the vinylidene monomer and(2) an interpolymer of the maleic monomer and the molecular weightregulator. It is also possible that an additional component of thepolymeric product may be an adduct formed between the maleic monomer andthe molecular weight regulator. Formulas I and 11 below illustrate themost probable structures of such adducts when the molecular weightregulator is terpinolene.

The above descriptions and particularly the examples are set forth byway of illustration only. Many other variations and modificationsthereof will be obvious to those skilled in the art and can be madewithout departing from the spirit and scope of the invention hereindescribed.

What is claimed is:

1. In a mass polymerization process for preparing a water soluble, lowmolecular Weight interpolymer from a mixture of 1 molar portion of amaleic monomer of the group consisting of maleic anhydride, maleic acid,half esters of maleic acid and a 1-18 carbon atom monohydric alcohol,and mixtures thereof, and 1-2 molar portions of at least 1 vinylidenemonomer interpolymerizable with said maleic monomer, the improvementwhich consists essentially of (1) heating the maleic monomer to atemperature of at least C., (2) agitating the maleic monomer, (3) addingthe vinylidene monomer to the maleic monomer at a rate not more thanabout 5 times the rate at which the added vinylidene monomer is beingpolymerized, (4) maintaining in the reaction mixture throughout theperiod of the addition of the vinylidene monomer at least about 0.5% byweight of a free radical generating polymerization initiator and from0.5 to 30% by weight of a molecular weight regulator, both of saidpercentages being based upon the vinylidene monomer that has been addedto the maleic monomer, and (5 maintaining the reaction mixture at atemperature of at least 100 C. until essentially all of the maleicmonomer and the vinylidene monomer have polymerized; said molecularweight regulator corresponding to the formula:

wherein R is a cyclic organic radical to which =CRR" is joined at acarbon atom of an alicyclic ring having at least 4 members, and whereinR and R" are independently selected from the group consisting ofhydrogen and n alkyl radical.

2. In a mass polymerization process for preparing a water soluble lowmolecular weight interpolymer from a mixture of 1 molar portion of amaleic monomer of the group consisting of maleic anhydride, maleic acid,half esters of maleic acid and a 1-18 carbon atom monohydric alcohol,and mixtures thereof, and 11.5 molar portions of at least one vinylidenemonomer interpolymerizable with said maleic monomer, the improvementwhich consists essentially of (1) heating the maleic monomer to atemperature of at least 100 C., (2) agitating the maleic monomer, (3)adding the vinylidene monomer to the maleic monomer at a rate not morethan about 5 times the rate at which the added vinylidene monomer isbeing polymerized, (4) maintaining in the reaction mixture throughoutthe period of addition of the vinylidene monomer about 1.04.0% by weightof a free radical generating polymerization initiator and about 5-20% byweight of a molecular weight regulator, both of said percentages beingbased upon the vinylidene monomer that has been added to the maleicmonomer, and (5) maintaining the reaction mixture at a temperature of atleast 100 C 7 until essentially all of the maleic monomer and thevinylidene monomer have polymerized; said molecular weight regulatorcorresponding to the formula:

R! R=C wherein R is a cyclic organic radical to which =CR'R" is joinedat a carbon atom of a alicyclic ring having at least 4 members, andwherein R and R" are independently selected from the group consisting ofhydrogen and an alkyl radical.

3. The process of claim 2 in which the molecular weight regulator isterpinolene.

4. A process of claim 2 in which the maleic monomer is maleic anhydrideand the vinylidene monomer is styrene.

5. The process of claim 2 in which the maleic monomer is at least onehalf ester of maleic acid and a 1-18 carbon atom monohydric alcohol andthe vinylidene monomer is styrene.

6. The process of claim in which the maleic monomer is methyl acidmaleate.

7. The process of claim 5 in which the maleic monomer is a mixture ofmethyl acid maleate and secondary butyl acid maleate.

8. The process of claim 5 in which the maleic monomer is the half esterof maleic acid and the mono-n-butyl ether of ethylene glycol.

9. In a mass polymerization process for preparing a Water soluble lowmolecular weight interpolymer from a mixture of 1 molar portion of amaleic monomer of the group consisting of maleic anhydride, maleic acid,a half ester of maleic acid and a 1-18 carbon atom monohydric alcohol,and mixtures thereof and 12 molar portions of at least one vinylidenemonomer interpolymerizable with said maleic monomer, the improvementwhich consists essentially of (1) heatnig to at least 100 C. the maleicmonomer which has dissolved therein at about 0.5 to by weight of amolecular regulator, said percentage being based upon the vinylidenemonomer to be added in step 3, (2) agitating the maleic monomer, (3)adding to the maleic monomer a vinylidene monomer which has dissolvedtherein at least about 0.5% by weight of a free radical generatingpolymerization initiator, the addition of the vinylidene monomer beingmade at a rate not more than about 5 times the rate at which the addedvinylidene monomer in being polymerized, and (4) maintaining thereaction mixture at a temperature of at least 100 C. until essentiallyall of the maleic monomer and the vinylidene monomer have polymerized;said molecular weight regulator corresponding to the formula:

R! R=O wherein R is a cyclic organic radical to which :CR'R" is joinedat a carbon atom of an alicyclic ring having at least 4 members, andwherein R and R are independently 8 selected from the group consistingof hydrogen and an alkyl radical.

10. In a mass polymerization process for preparing a water soluble, lowmolecular weight interpolymer from a mixture of 1 molar portion of amaleic monomer of the group consisting of maleic anhydride, maleic acid,half esters of maleic acid and a 1-18 carbon atom monohydric alcohol,and mixtures thereof, and 11.5 molar portions of at least one vinylidenemonomer interpolymerizable with said maleic monomer, the improvementwhich consists essentially of (1) heating to at least C. the maleicmonomer which has dissolved therein about 520% by weight of a molecularweight regulator, said percentage being based upon the vinylidenemonomer to be added in step 3, (2) agitating the maleic monomer, (3)adding to the maleic monomer a vinylidene monomer which has dissolvedtherein about 1.04.0% by weight of a free radical generatingpolymerization initiator, the addition of the vinylidene monomer beingmade at a rate not more than about 5 times the rate at which the addedvinylidene monomer is being polymerized, and (4) maintaining thereaction mixture at a temperature of at least 100 C. until essentiallyall of the maleic monomer and the vinylidene monomer have polymerized;said molecular weight regulator corresponding to the formula:

R! R=C RII wherein R is a cyclic organic radical to which :CRR" isjoined at a carbon atom of an alicyclic ring having at least 4 members,and wherein R and R" are independently selected from the groupconsisting of hydrogen and an =a1kyl radical.

11. The process of claim 10 in which the molecular rate regulator isterpinolene.

12. The process of claim 10 in which the maleic monomer is maleicanhydritle and the vinylidene monomer in styrene.

13. The process of claim 10 in which the maleic monomer is at least onehalf ester of maleic acid and a 1-18 carbon atom monohydric alcohol andthe vinylidene monomer is styrene.

14. The process of claim 13 in which the maleic monomer is methyl acidmaleate.

15. The process of claim 13 in which the maleic monomer is a mixture ofmethyl acid maleate and secondary butyl acid maleate.

16. The process of claim 13 in which the maleic monomer is the halfester of maleic acid and the mono-nbutyl ether of ethylene glycol.

17. The product of the process of claim 1.

References Cited UNITED STATES PATENTS 2,383,399 8/1945 Lundquist26093.3 2,556,488 6/1951 Wakeford et al 26093.3

JOSEPH L. SCHOFER, Primary Examiner.

J. KIGHT, Assistant Examiner.

